~?S'.  i*+  ^ 


U.  S.  DEPARTMENT  OF  AGRICULTURE, 

BUREAU  OF  ENTOMOLOGY     CIRCULAR  No.  143. 

*    L.  O.   HOWARD.  Kniomologiu  *nd  Chief  of  Burcu 


INSECT  DAMAGE  TO  STANDING  TIMBER 
IN  THE  NATIONAL  PARKS. 


A.   I).   HOPKINS, 

In  Charge  of  V  jationM. 


■  —Or.  1 1 


WASHi:  IK\I    PBINTIKO  OmC*  :  1013 


/.'  /  BEAU   OF    E  V TO  \tOL (> Q  V. 

L.  O.  HOWABD,  Entomologist  and  Chief  of  Bureau. 
('.  L.  Maui  att.  Entomologist  and  Acting  Chief  in  Absence  of  Chief. 

U.    S.    CLIFTON,    linen  tire    Assistant. 
W.  V.  Tastit.  Chief  Clerk. 

F.  H.  Chittenden,  in  charge  of  truck  crop  and  stored  product  insect  investigations. 

A.  1).  Hoi-kins,  in  charge  of  forest  insect  inrestigations. 
W.  I>.  HUNTER,  in  charge  of  southern  field  crop  insect  inrestigations. 
P.  M.  WEBSTER,  in  Charge  of  cereal  and  forage  insect  inrestigations. 
A.  L.  QuAlNTANCE,  in  charge  of  deciduous  fruit  insect  investigations. 
E.  F.  Fiiijli.ii's.  in  charge  of  bee  culture. 

D.  M.  Rogers,  in  charge  of  preventing  spread  of  moths,  field  work. 
Koli.a  P.  CUBBIE,  in  charge  of  editorial  work. 

Mabkl  Polcord,  in  charge  of  library. 

Forest  Insect  Investigations. 
A.  D.  Hopkins,  in  charge. 

H.  E.  Burke,  entomological  assistant,  in  charge  of  Forest  Insect  Field  Station  S, 

Yreka,  Cal. 
W.  T).  Edmonston,  agent  and  expert,  in  charge  of  Forest  Insect  Field  station  G. 

Klamath   Falls,  Orcg. 
Josef  Brunner.  agent  and  expert,  in  charge  of  Forest  insect  Field  station.   I. 

Columbia    Falls,    Mont. 

E.  B.  Mason,  entomological  assistant,  in  charge  of  Forest  Insect  Field  Station  ?. 
Spartanburg.  S.  G. 

T.  F.  Snyder,  agent  and  expert,  engaged  in  investigations  of  insect  damage  to 

telegraph  and  telephone  poles. 
J.  L.  Webb,  entomological  assistant,  specialist  on  cerambgcid  beetles  and  larva. 
S.  A.  RoHWER,  agent  and  expert,  specialist  on  sawflics   i  Tenthredinoidea). 
Mary  F.  Fatjnce,  Mary  C.  Johnson,  Maude  Taylor,  Elizabeth  Ritchie,  pre- 

parators. 
ii 


Circular  No.  143. 

United  States  Department  of  Agriculture, 

BUREAU   OK   ENTOMOLOGY. 
L.  O.   HOWARD,   KntomoloKin  and  Chief  of  Bureau. 


INSECT  DAMAGE  TO  STANDING  TIMIiKK  IN  TIM! 
NATIONAL  PARKS.  ' 

I'.y   A.    I  >.    IlorKis-. 

in  t'luiiiji  nf  Forest  Insect  Investigations. 
CHARACTER  OF  THE  DAMAGE. 

The  damage  by  insects  to  the  living  trees  of  the  forests  and  orna- 
mental grounds  of  the  national  parks  consists  of  injuries  to  the 
foliage,  branches,  or  the  entire  tree  which  mar  or  destroy  their 
attractive,  educational,  and  historic  features  and  diminish  <>r  destroy 
their  commercial  \  alue. 

Throughout  the  forests  of  the  Rocky  Mountains  and  Pacific  slope, 
including  the  national  parks,  a  large  percentage  <d"  the  timber  has 
died  during  the  past  half  century.  The  old  standing  and  fallen  dead 
.  tlu*  red  foliage  of  those  that  died  last  year,  and  the  fading 
tops  of  those  now  dying  bear  evidence  of  the  work  of  insects  and 
are  conspicuous  example-,  of  a  great  waste  of  forest  resources.  In 
some  localities  a  few  scattering  tree-  die  each  year  within  a  town- 
ship or  section;  in  other-,  clumps  of  tree-  or  whole  forests  die  during 
a  -ingle  year. 

The  conifer-,  which  are  the  predominating  trees  of  this  western 
part  of  the  country,  are  subject  to  a  high  death  rale  from  insect 
attack-.  The  pine-,  ihe  -pruce-.  the  Douglas  tir.  the  balsam  firs, 
the  hemlock-,  the  cedars,  and  the  Sequoia-   (redwood-)   have  each  at 

least  one  destructive  enemy. 

In  the  fall,  spring,  and  early  summer  the  dying  and  recently  dead 

are  conspicuous  on  account  of  their  fading,  yellowi-h-red.  and 

reddish-brown   foilage,  as  if  injured  by  fire.     When  they  are  in 

large    patches,   or   extend   over   a    considerable   area,   their   death    i- 

often  attributed  by  the  casual  observer  to  forest  fin 

•This  paper  was  md  l>y  the  author  at  a  eonferrnre  of  national  park  superintendent* 
held  iinii.r  the  eosplcea  of  the  Secretary  of  the   Interior,  September   11—12,    mil.  and 

Is  embodied   in   Hie  prow-dins*  of  the  meeting  Issued   Ux   the   Interior  Department 


2  INSECT    DAMAGE   IN    THE    NATIONAL   PARKS. 

EXTENT   OF   THE  DAMAGE. 

The  extent  of  the  damage  to  the  forests  by  insects  through  the 
accumulation  of  dead  timber  and  the  dying  of  matured  trees  over 
large  areas  is  vastly  greater  than  the  general  observer  would  suppose. 
In  fact,  the  dead  and  fallen  timber  is  so  common  in  all  forests  that 
it  has  heretofore  been  recognized  as  a  natural  and  inevitable  condi- 
tion. Large  areas  of  insect-killed  timber  have  been  charged  to  fire 
without  further  thought  or  examination  to  determine  the  real  cause. 
Fallen  timber  has  been  attributed  to  storms,  and  scattering  dead 
trees  to  old  age. 

During  the  present  year  a  reconnaissance  was  made  of  typical 
sections  in  one  of  the  national  forests,  where  there  was  no  evidence 
that  destructive  forest  fires  had  occurred  during  the  past  20  year^. 
It  was  found  that  the  standing  and  fallen  dead  yellow  pine  that 
had  died  within  that  period  amounted  in  board  feet  to  nearly  half  as 
much  as  that  which  was  then  living,  and  of  the  sugar  pine  and 
Douglas  fir  there  was  one-fourth  as  much  dead  as  was  ihen  living, 
and  every  dead  tree  examined  in  the  estimate  showed  evidence  that 
it  had  been  killed  by  insects. 

In  the  Black  Hills  National  Forest  of  South  Dakota  over  one-half 
of  the  timber  died  within  a  period  of  about  10  years.  In  Oregon 
and  Montana  nearly  all  of  the  larger  pine  died  within  a  few  years 
on  areas  of  a  few  hundred  acres  to  100,000  acres  or  more.  These 
together  with  many  other  examples  of  extensive  dying  of  timber 
have  been  investigated  and  found  to  be  caused  primarily  by  insects. 
Investigations  have  also  demonstrated  beyond  question  that  a  vast 
amount  of  timber  is  killed  by  insects  every  year  within  the  forested 
areas  of  the  Eocky  Mountain  and  Pacific  Coast  regions.  Further- 
more, the  accumulation  of  this  dead  timber  and  fallen  debris  is  a 
menace  to  the  living,  because  it  furnishes  fuel  for  destructive  forest 
fires.  The  losses  from  insect  depredations  are  thus  augmented  by 
fires. 

The  extent  of  damage  to  the  forest  and  other  trees  of  the  national 
parks  has  not  been  estimated  and.  with  the  exception  of  investigations 
conducted  in  the  Yosemite  and  Glacier  Parks,  we  do  not  have  much 
direct  information  as  to  the  damage  already  done.  It  is  plain  to  us, 
however,  that  the  general  conditions  are  not  different  from  those 
which  prevail  throughout  the  regions  in  which  the  parks  are  located 
and  in  which  the  destructive  species  of  insects  are  known  to  occur. 

The  amount  of  damage  in  the  parks  must  be  considered  not  only 
on  the  basis  of  the  commercial  value  of  the  forest  resources,  but  on 
that  of  the  aesthetic  and  educational  value  of  the  virgin  forest  with  its 
typical  examples  of  tree  species. 

The  loss  of  a  section  of  the  forest  which  forms  the  attractive  fea- 
ture in  the  landscape,  or  is  the  only  remaining  example  of  the  origi- 


lN.-it   i    DAMAG1     in     Mil     NATIONAL   PABKS.  'A 

nal  i  \  | ic  df  foresl  growth  of  thai  region,  i->  far  greater  than  that  rep 
resented  by  the  commercial  value  of  the  timber;  a-  i-  also  tin-  loss  of 
notable  veterans  and  giante  of  the  different  species.    These  old  I'm' 
and  old  trees  are  at  present  one  of  the  attractive  and  instructive  fea 
(nil-  'if  the  timbered  areas  of  some  of  the  national  parks,  and  if  they 
■re  protected  from  their  insect  and  other  enemies  thej  will  Ik4  even 
more  attractive  features  in  coming  centuries.     Under  present  condi- 
tions, these  "M  trees  of  the  virgin  forest  are  in  greater  danger  «»f 
being  killed  by  insects  than  are  the  younger  trees.     Indeed,  many  of 
them  have  been  killed  within  recent  years. 

The  three  -.riant  sugar  pine-  on  the  nail  from  Wawona  to  Glacier 
Point  and  the  Yosemite  Valley  air  examples.  Two  of  them  w< 
■  lead  and  the  other  was  dying  when  I  -aw  them  in  June.  l'.'Ok  and 
there  was  Conclusive  evidence  that  their  death  W8S  cau-ed  l>\  the 
mountain  pine  beetle.  The  veteran  Sugar  pine,  known  a-  "  I'nele 
Tom,"  was  being  attacked  at  thai  time  by  the  Bame  species  of  beetle, 
and  I  am  informed  that  it  died  the  following  year.  The  loss  of  tl 
four  Lriant>  of  the  species  i>  irreparable. 

The  Sequoias  are  supposed  to  he  immune  to  the  attack  of  insects, 
hut  they  are  not.  They  are  more  resistant  than  other  species,  ami 
that  i-  one  reason  they  have  lived  so  long.  However,  each  species 
ha-  a  barkbeetle  enemy  which,  under  favorable  condition-,  i-  capable 
of  killing  the  largest  and  finest  specimens.  I  safi  one  of  the  large 
redwoods  in  the  vicinity  of  Eureka,  Cal.,  that  had  been  killed  by  its 
barkbeetle  enemy,  and  when  in  the  Mariposa  Grove,  in  1904,  I  dis- 
covered the  barkbeetle  enemy  of  the  big  tree  in  the  living  hark  of  a 
storm-broken  limb. 

THE    PRINCIPAL    DEPREDATORS. 

The  mere  mention  of  the  name-  of  the  thousands  of  species  of  in- 
sects, each  of  which  causes  some  peculiar  injury  during  the  life  of  the 
different   tree  species,  would  occupy  more  -pace  than   i-  allotted    for 

this  paper.  Therefore  we  must  consider  the  more  important  of  those 
which  are  directly  responsible  for  the  death  of  the  tree-. 

The  little  genus  of  Dendroctonus  beetles,  of  tree-killing  hectic-,  is 
represented  in  the  Rocky  Mountain  and  Pacific  Slope  regions  by  a 
few  species  which  are  more  destructive  to  the  conifer-  of  western 
North  America  than  all  other  forest  insects  combined.  They  are  a 
constant  menace  to  the  pine,  spruce,  and  Douglas  fir  of  the  national 
park-.  They  are  certain  to  he  present  in  every  park  in  which  there 
arc  forests  of  their  hosl  tree-,  and  have  doubtless  caused  far  greater 
damage  than  the  park  officials  have  realized. 

The  species,  in  the  order  of  their  destructiveness.  are  the  mountain 
pine  beetle,  the  western  pine  beetle,  the  Bngelmann  spruce  beetle,  the 


4  INSECT   DAMAGE    IX    THK.    NATIONAL  PARKS. 

Jeffrey  pine  beetle,  and  the  red  turpentine  beetle.  All  but  the  Jeffrey 
pine  beetle  of  the  Sierras  are  common  to  the  northern  Rocky  Moun- 
tains and  the  Pacific  Slope.  Those  common  to  the  central  and  south- 
ern Rocky  Mountains  are  the  Black  Hills  beetle,  the  Engelmann 
spruce  beetle,  the  Douglas  fir  beetle,  and  the  red  turpentine  beetle. 
There  are  three  other  species  common  to  the  southern  Rocky  Mount- 
ains and  northern  Mexico  which  are  of  less  importance  in  causing 
the  death  of  trees. 

These  insects  are  small,  stout,  black  to  reddish-brown  beetles,  rang- 
ing in  length  from  about  2  mm.  to  9  mm.,  or  0.0S  to  0.30  of  an  inch. 
They  fly  in  the  period  from  April  to  October  and  attack  the  main 
trunks  of  the  living  healthy  trees  by  boring  into  the  bark  and  ex- 
cavating long  winding  or  nearly  straight  egg  galleries  between 
the  bark  and  wood.  In  this  manner  they  completely  girdle  and  thus 
cause  the  death  of  their  victims.  As  soon  as  the  bark  begins  to  die  the 
eggs  deposited  by  the  beetles  hatch  and  the  young  grubs,  or  larval 
forms,  complete  the  destruction  of  the  inner  bark.  All  of  the  broods 
develop  into  the  adult  stage  within  a  year  and  emerge  from  the 
bark  to  fly  in  search  of  new  victims.  Each  species  ha-  its  peculiar 
habits  in  the  choice  of  host  trees,  methods  of  attack,  and  period  of 
development. 

THK   MOUNTAIN   PINK  BKKTKE. 

The  mountain  pine  beetle  attacks  the  mountain  or  silver  pine,  sugar 
pine,  western  yellow  pine,  lodgepole  pine,  and  evidently  all  other 
pines  of  the  northern  Rocky  Mountains  and  the  Pacific  slope.  The 
adult  beetles  fly  in  the  period  from  July  to  October,  inclusive.  When 
abundant  they  concentrate  their  attack  on  clumps  and  patches  of 
trees.  Their  long,  nearly  straight  egg  galleries  and  radiating  larval 
mines  soon  kill  the  bark  on  the  main  trunks,  but  the  foliage  of  the 
infested  trees  remains  green  and  apparently  healthy  until  the  follow- 
ing May  and  June.  It  then  begins  to  change  to  a  pale  green  and 
later  to  yellowish  and  brown.  By  the  time  all  of  the  foliage  is  dead, 
about  the  1st  of  July,  the  overwintered  broods  of  beetles  begin  to 
emerge.  By  the  middle  of  August  most  of  them  are  out  of  the  dead 
trees  and  have  entered  the  living  ones. 

This  is  by  far  the  most  destructive  insect  enemy  of  the  pine  within 
its  range,  and  under  present  conditions  is  a  constant  menace  to  the 
forests  of  matured  or  merchantable-sized  timber.  It  can  be  con- 
trolled by  felling  the  infested  trees  and  by  removing  the  infested 
bark  from  the  main  trunks  without  burning  the  bark  or  tops.  This 
work  must  be  done  during  the  period  between  the  1st  of  October  and 
the  1st  of  July  to  destroy  the  broods  of  the  beetle  before  they  emerge. 
"Whenever  the  timber  can  be  utilized  the  product  will  pay  all  ex- 
penses.    If  it  has  no  commercial  value  it  will  cost  on  an  average 


IN.-M    i    DAMAGI     IN    Till     NATIONAL    PABKB.  5 

50  cents  :>  tree  for  the  reipiired  treatment,  After  an  outbreak  is 
under  control  the  living  timber  can  be  easily  protected  from  further 
depredations  by  giving  prompt  attention  to  the  felling  and  barking 
of  any  clumps  of  dying  trees  found  during  May  and  June  Rang 
or  lire  patrolmen  can  be  instructed  so  thai  they  can  il<>  this  and  any- 
thing else  thai  is  required  t<>  maintain  control. 

Mil       ¥  I  -  I  M.N      l-l  \1      Bl   I    II   I  . 

The  western  pine  beetle  attacks  the  western  yellow  pine,  the  sugar 
pine,  and  the  Jeffrey  pine  The  hectic-  fly  in  late  June  t<>  Octol 
inclusive,  and  usually  attack  scattering  individual  trees,  often  select- 
ing the  larger  and  older  examples.  The  adults  excavate  winding 
egg  galleries  between  the  inner  living  bark  and  the  wood  and  trans- 
form to  the  adult  stage  in  the  outer  bark.  The  beetles  begin  («>  fly 
and  attack  the  tree-  in  dune  and  continue  the  attack  until  October  or 
November.  The  first  generation  develops  and  emerges  in  August  to 
November,  and  the  second  generation  passes  the  winter  in  the  tri 
that  are  killed  by  it  in  the  summer  and  tall. 

The  foliage  of  the  infested  trees  begins  bo  lade  and  ftUm  yellow  in 
a  few  weeks  after  the  trees  are  attacked  by  this  hectic.      The  summer 

broods  <>f  the  first  generation  leave  the  trees  by  the  time  the  foliage 

is  reddish  htow  n.  hut  the  o\  erw  intered  broods  do  not  emerge  until  the 
following  May  ami  dune,  in  some  cases  Several  months  after  'he 
foliage  is  brown. 

Thi>  Specie:  is  next  in  importance  to  the  mountain  pine  beetle 
.1  destructive  enemy  of  the  pine,  and  the  two  special  often  combine 
in  their  attack.  In  this  combined  attack  the  wesiera  pirn  hectic  is 
a  secondary  enemy  of  the  trees  Decease  it  follow-  the  attack  of  the 
other  species.  When  it  is  the  primary  enemy  it  i-  responsible  for 
the  death  of  a   few    BCattering  tree-  each  year  throughout   the   foiv-t. 

which  results  in  the  accumulation  of  dead  timber.     In  the  aggre- 
gate, tlii-  accumulative  loss  i-  very  extensive,  involving,  as  it  does,  the 
largest  and  best  trees. 
The  insect  can  Iw  controlled  and  the  living  timber  protected  from 
by  felling  the  infested  trees  during  the  period  between  the 

1st  of  October  and  the  Lai  of  June  and  removing  the  hark-  from  the 
main  trunks  and  burning  it.  It  is  necessary  to  hum  the  hark  because 
the  broods  of  this  species  transform  in  the  outer  hark.  They  are  not 
destroyed  by  -imply  exposing  the  inner  hark,  a-  i-  the  ca-c  with  the 
mountain  pine  hectic. 

Mil     -1  KI  KKKV    lMNh     CI  I    111. 

The  characteristic  habits  of  the  Jeffrey  pine  hectic  are  similar  to 
those  of  the  mountain  pine  beetle,  and  therefore  it  requires  the  same 
treatment. 


6  INSECT   DAMAGE   IN   THE   NATIONAL  PARKS. 

THE  DOUGLAS  FIR  BEETLE. 

The  Douglas  fir  beetle  attacks  the  Douglas  fir,  the  big-cone  spruce, 
and  the  western  larch.  The  beetles  fly  in  April  and  May  and  enter 
the  living  bark  on  healthy  trees  and  on  trees  that  have  been  injured 
by  fire  and  those  that  have  been  recently  felled.  In  habits  of  attack 
and  general  characteristics  the  Douglas  fir  beetle  is  similar  to  the 
mountain  pine  beetle,  except  that  the  former  begins  to  fly  earlier 
in  the  season  and  the  foliage  of  the  trees  infested  b<jgin>  to  die  in 
the  fall.  It  is  very  destructive  to  the  Douglas  fir  throughout  the 
Rocky  Mountain  region  from  British  Columbia  to  Mexico,  but  is 
much  less  so  on  the  Pacific  slope,  especially  toward  the  coast.  It 
can  be  controlled  by  felling  the  infested  trees  during  the  period 
between  the  1st  of  September  and  the  1st  to  middle  of  the  following 
April  and  removing  the  infested  bark  from  the  trunks  without 
burning. 

THE  RED  TURPENTINE  BEETLE. 

The  red  turpentine  beetle  is  the  largest  species  of  the  genus  Den- 
droctonus.  It  begins  to  fly  in  April  and  is  active  until  October  and 
November.  It  attacks  the  pine  and  rarely  the  spruce.  As  a  rule  it 
confines  its  operation  to  the  base  or  basal  portion  of  the  trunk-. 
While  its  normal  habit  is  to  breed  in  the  bark  of  stumps  and  logs  of 
newly  felled  trees,  it  often  infests  the  bark  on  healthy  trees.  It 
rareh7  kills  a  tree,  but  is  the  cause  of  a  large  percentage  of  the  basal 
wounds  known  as  "cat  faces"  and  fire  wounds,  so  commonly  met 
with  in  the  pine.  This  is  a  far  more  difficult  species  to  control  than 
the  others  because  it  breeds  in  the  stumps  of  felled  trees  and  the  1 
of  those  killed  by  the  other  species  or  by  fire.  Valuable  individual 
trees  can  be  protected  by  cutting  the  beetles  out  of  the  bark  as  soon  ;i- 
their  presence  is  indicated  by  masses  of  exuding  resin  mixed  with 
reddish  boring  dust. 

Wherever  there  are  continued  lumbering  operations  the  red  turpen- 
tine beetle  confines  its  attack  to  the  stumps,  but  in  the  national  parks 
and  private  grounds  where  a  limited  amount  of  timber  is  cut,  or 
where  the  ravages  of  the  mountain  pine  and  western  pine  beetles 
have  been  controlled,  it  is  likely  to  cause  more  or  less  extensive  dam- 
age to  the  living  timber  for  a  year  or  two  after. 

In  combating  the  other  beetles  in  the  national  parks,  care  should 
be  taken  to  remove  the  bark  from  the  stumps  whenever  they  are 
found  to  be  infested  with  this  pest. 

THE  ENGELMANN  SPRUCE  BEETLE. 

The  Engehnann  spruce  beetle  attacks  the  Engelmann  spruce,  blue 
spruce,  and  any  other  species  of  spruce  found  within  its  range,  but 


INSKCI    DAMAG1     IN    THE    NATIONAL    PA1  7 

does  not  attack  the  pine.  Douglas  fir,  or  balsam  fir.  I(  flies  in  the 
period  from  June  to  August  and  attacks  the  bark  of  the  main  trunks 
of  the  ulilcr  or  matured  tree-,  h-  habits  are  Bimilar  to  those  of  the 
mountain  pine  beetle,  except  that  it  flies  earlier  in  the  spring.  When 
the  trees  begin  to  die  the  needles  fade  to  a  pale  green  and  fall  before 
they  change  to  yellow  or  brown,  but  the  bare  tw  igs  present  a  grayish- 
brown  appearance.  The  infested  trees  are  easily  Located  in  the  fall 
;iikI  early  Bpring  by  the  fallen  needles  and  the  bare  twigs  of  the  tops. 
This  species  occurs  from  British  Columbia  to  Mexico  and  at 
times  is  rery  destructive  to  the  Engelmann  spruce  forest-.  It  can 
l>e  controlled  by  felling  the  infested  trees  and  removing  the  bark 
from  the  main  trunk-  during  the  period  beginning  with  the  1st  of 
October  and  ending  by  the  middle  to  last  of  May. 

I  ill:    r.i.\<  K    Mil. is    i;i  I  mi. 

The  Black  Hills  beetle  is  by  far  the  most  destructive  insect  enemy 

of  the  pine  of  the  central   and  southern    Rocky   Mountain-   and   the 
Black  Hills  of  South  Dakota.     It-  habits  are  similar  to  those  of  the 

mountain    pine   beetle,    and    the    -ame    method-    are    adopted    for   its 
control. 

FAVORABLE  CONDITIONS  FOR  THE  BEETLES. 

There  are  certain  conditions  in  the  administered  a-  well  as  in  the 
natural  forests  which  contribute  to  the  multiplication  and  destructive 
\\  ork  of  these  1  'end  rod  onus  heet  I es.  One  of  the  most  favorable  con- 
ditions is  an  extensive  forest  of  matured  and  old  trees  of  pine  or 
b]  nice,  because  in  the  beginning  of  an  invasion  such  trees  are  more 
often  the  lirst  to  be  attacked  and  killed.  Trees  in  such  a  forest 
injured  by  lightning  or  storms  often  form  center-  of  infestation  in 
which  the  beetles  increase  to  sufficient  numbers  to  enable  them  to 
kill  a  few  trees,  and  then  the  invasion  i-  started,  year  after  year 
increasing  in  force  until  a  large  percentage  or  all  of  the  old  timber  is 
killed.  The  hectics  then  attack  the  young  trees  and  often  waste  their 
energies  on  saplings,  in  which  the  broods  fail  to  develop. 

Drought. — It  is  a  common  belief  that  severe  droughts  weaken  the 
and  tin;-  contribute  to  favorable  condition-  for  the  attack  of  the 
beetles.  We  have  made  a  \ery  thorough  investigation  of  this  sub- 
ject and  are  led  to  conclude  that  exceptionally  dry  seasons  are  more 
unfavorable  for  the  development  of  the  beetles  than  are  moderately 
humid  one-,  and  that,  therefore,  droughts  do  not  contribute  to  their 
multiplication. 

Forest  fires. — Forest  fires  contribute,  to  a  limited  extent,  to  the 
multiplication  of  certain  species  which  breed  in  fire-scorched  tree-. 
but  as  a  rule  forest  tire-  kill  more  beetles  than  they  protect. 


8  lXSKCT  L).\M.u;i-    tn   the   national  pakks. 

Coinmi  rc'iiil  cutting. — Commercial  cutting  of  timber  may  contrib- 
ute to  the  multiplication  of  certain  species  which  breed  in  the  stump.- 
and  tops,  but  if  the  cutting  is  continuous  the  insects  confine  then- 
attack  to  the  cut-over  areas  and  do  not  invade  the  living  timber. 
Sporadic  summer  cutting,  however,  is  dangerous.  The  odor  of  the 
cut  wood  attracts  the  flying  beetles  to  the  locality.  This  contributes 
to  their  concentration,  and  when  the  cutting  is  stopped  they  invade 
the  living  timber. 

Secondary  enemies. — The  secondary  enemies  of  the  trees  consist  of 
numerous  species  which  attack  the  bark  and  wood  as  soon  as  the 
trees  become  weakened  and  are  dying  from  other  causes.  The  Den- 
droctonus  beetles  are  the  primary  enemies  or  leaders  in  the  attack. 
The  secondary  enemies  are,  to  a  certain  extent,  their  allies,  and 
when  very  abundant  may  contribute  to  favorable  conditions  for 
rapid  advance  in  the  destructive  movement,  but  more  often  they 
are  dependents  and  scavengers,  merely  utilizing  the  dead  and  wa-te 
material.  With  rare  exceptions  these  secondary  enemies  are  not 
capable  of  killing  trees  on  their  own  account. 

UNFAVORABLE  CONDITIONS  FOR  THE  BEETLES. 

The  unfavorable  conditions  for  the  destructive  work  of  these 
Dendroctonus  beetles  are  to  be  found  in  administered  forests  where 
the  ripe  or  matured  timber  is  utilized  and  where  the  young  timber 
is  protected  by  the  prompt  disposal,  during  the  fall,  winter,  and 
spring  months,  of  any  clumps  of  d}-ing  trees. 

In  other  words,  systematic  forest  management  based  on  a  knowl- 
edge of  the  principles  of  silviculture  and  forest  entomology  will 
soon  present  conditions  so  unfavorable  for  the  Dendroctonus  beetles 
that  thev  can  no  longer  exist  as  agents  of  destruction  and  waste. 

The  natural  enemies  of  the  beetles  serve  as  a  repelling  force  against 
the  progressive  development  of  an  invasion.  Indeed,  they  are  among 
the  principal  factors  which  have  prevented  the  extermination  of 
certain  of  the  more  important  forost-tree  species.  These  natural 
enemies  consist  of  parasites  and  predatory  insects,  which  feed  on 
all  stages  of  the  barkbeetles,  and  birds,  which  feed  on  the  adults 
and  young  of  the  barkbeetles.  Were  it  not  for  the  fact  that  birds 
also  feed  on  the  predatory  and  parasitic  insect  enemies  of  the  bark- 
beetles, and  that  such  birds  are  limited  in  numbers,  the}7  might  render 
the  great  service  that  is  so  commonly  credited  to  them. 

Insect  diseases  in  the  form  of  epidemics  sometimes  serve  to  bring 
an  invasion  under  complete  control,  and  unfavorable  climatic  con- 
ditions have  been  known  to  exterminate  a  species  of  Dendroctonus 
beetles  within  an  area  of  thousands  of  square  miles. 

Therefore,  although  under  natural  conditions  successive  genera- 
tions of  the  older  trees  are  killed  by  their  insect  enemies,  these  in 


IN  SIC  I      l>\\|\t.l       IN      I  II  I       \  M '  1  •  i  N  Hi     l'\.  9 

turn  em  checked  or  repelled  by  natural  means,  bo  that  generations 
of  younger  trees  take  tin-  place  of  their  anc  tnd  the  feces!  m 

such  l-  perpetuated. 

Natural  iniifrn/  tkt  In   thfl   national   park-,  na 

tional  forests,  and  private  foreete  where  the  n  icommer- 

cial  vain*  this  natural  eontrol  of  the  insect  depredators  on  1 1 1  *  - 
timber  is  the  mod  expensive  and  wasteful  Our  friends,  the  enemies 
of  the  beetles,  can  not  be  depended  upon  to  operate  for  the  besl 
interests  of  the  Federal  or  private  owner.  They  can,  however,  be 
made  to  render  efficient  service  as  tin'  allies  of  the  oi  osr  in  an  aggres- 
sive warfare  by  him  againsl  the  invaders  In  1 1  * i  — -  capacity  they  are 
indispensable  in  the  defense  against  renewed  attacks  and  in  1 1 1  *  -  main 
tenaace  of  conditions  which  will  insure  the  future  protection  of  the 
living  timber. 

GENERAL   METHODS    OF    CONTROL. 

It  is  through  a  knowledge  of  the  habits  and  seasonal  history  of  the 
various  species  of  depredating  insects,  and  the  various  complex  fac- 
tors operating  Cor  and  against  them,  thai  forest  entomologists  arc 
enabled  to  advise  methods  of  procedure  in  practical  control  opera- 
tions either  to  reduce  or  eliminate  the  favorable  conditions  for  the 
multiplication  of  the  beetles  or  to  promote  and  utilize  the  factors 
that  are  unfavorable  for  their  existence. 

It  is  also  through  a  knowledge  of  the  characteristic  evidences  of 
their  preeence  in  the  living  and  dying  trees  that  we  are  enabled  to 
give  instructions  to  an  experienced  timber  cruiser,  forest  ranger,  or 
fire  patrolman  which  will  enable  him  readily  to  detect  an  infestation 
and  report  upon  its  character  and  extent. 

Experiments  with  and  demonstrations  of  methods  of  control  have 
furnished  up-to-date  information  on  the  essential  requirements  in 
conducting  active  control  operation-,  which  enables  ns  to  advise  the 
most  economical  and  effectual  method  to  be  adopted  for  each  species 
of  beetle,  each  species  of  tree,  and  each  locality  where  an  infestation 
prevails. 

Therefore,  if  the  symptoms  are  accurately  described  and  informa- 
tion is  furnished  as  to  the  local  facilities  for  utilizing  the  infested 
timber  or  for  treatment  at  direct  expense,  specific  recommendation-, 
successful   control   can   he   made   without    an   examination   by   an 

expert 

The  presence  in  any  national  park  of  quantities  of  dying  pine. 
spruce,  or  Douglas  fir  that  has  not  been  caused  by  recent  fir 
evidence  of  the  presence  and  destructive  work  of  one  or  more  species 
of  the  Dendroctonus  beetles.  An  examination  of  the  bark  of  the 
main  trunks  of  some  of  the  dying  tree-  will  usually  furnish  conclusive 
evidence,  for  if  the  trees  are  infested  the  characteristic  work  in  the 


UNIVERSITY  OF  FLORIDA 


3  1262  09216  6122 

10  INSECT  DAMAGE   IX    THE    XATIC . .„. 

bark,  as  illustrated  in  the  bulletins  of  the  Bureau  of  Entomology,  will 
be  easily  recognized. 

The  next  thing  to  do  is  to  determine  the  extent  of  the  infestation, 
the  kind  of  trees  involved,  and  the  facilities  for  disposing  of  the 
timber  by  sale,  free  use,  or  direct  exjjense.  Then  the  superintendent 
should  report  the  facts  to  an  expert  and  ask  for  advice  and  recom- 
mendations. If  he  will  then  proceed  without  delay  to  dispose  of  the 
infestation  according  to  instructions  given  him,  success  in  checking 
or  completely  controlling  the  pest  is  almost  certain  to  follow. 

If,  upon  locating  an  infested  area,  it  is  found  to  extend  beyond  the 
park  boundary  into  adjacent  privately  owned  timber  or  the  national 
forests,  cooperation  or  at  least  concerted  action  is  required,  because 
an  important  center  of  infestation  is  a  menace  to  the  living  timber 
within  a  radius  of  10  to  20  miles. 

If  the  timber  of  a  national  park  is  healthy  and  centers  of  infesta- 
tion are  found  in  adjacent  forests  within  a  radius  of  10  to  20  miles, 
the  park  superintendent  should  notify  the  owners.  If,  for  any 
reason,  the  owners  can  not  dispose  of  the  infestation  the  park  officials 
should  help  do  it  just  as  they  would  help  in  fighting  a  fire  that 
was  threatening  the  park.  In  like  manner  the  Federal  and  private 
owners  of  healthy  timber  adjacent  to  a  park  should  help  dispose  of 
any  extensive  infestation  in  the  park,  because  it  may  be  more  of  a 
common  menace  than  a  forest  fire. 

If  this  policy  of  cooperation  for  the  general  good  is  adopted  and 
the  essential  requirements  for  successful  control  are  strictly  adhered  to 
for  a  few  years  by  the  officials  of  the  national  parks,  the  national 
forests,  and  the  principal  private  owners,  the  damage  to  living 
timber  in  the  parks  and  on  adjacent  lands  will  be  reduced  to  a  mini- 
mum, and  ultimately  thousands  of  dollars  in  commercial  and  aesthetic 
values  will  be  saved  for  every  dollar  of  public  or  private  money 
expended. 


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